Process for developing photographic elements

ABSTRACT

1. IN A PROCESS OF DEVELOPING AN IMAGEWISE-EXPOSED PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT AND AT LEAST ONE IMAGE DYE-PROVIDING LAYER UNIT THEREON WHICH CONTAINS A LIGHT-SENSITIVE SILVER HALIDE EMULSION HAVING ASSOCIATED THEREWITH A COLOR COUPLER, WHICH PROCESS INCLUDES (1) DEVELOPMENT OF THE IMAGEWISE-EXPOSED SILVER HALIDE EMULSION TO PROVIDE AN IMAGEWISE DISTRIBUTION OF METALLIC SILVER AND INBIBITION OF A COLOR-DEVELOPING AGENT IN SAID PHOTOGRAPHIC ELEMENT, AND THEN (2) CONTACTING SAID PHOTOGRAPHIC ELEMENT WITH AN AMPLIFIER COMPOSITION WHICH REPRESSURES SUBSTANTIALLY ADITIONAL NET SILVER DEVELOPMENT, SAID AMPLIFIER SOLUTION CONTAINING A COBALT(III) METAL COMPLEX HAVING A CORDINATION NUMBER OF 6, AND SAID AMPLIFIER SOLUTION BEING MMAINTAINED IN CONTACT WITH SAID PHOTOGRAPHIC ELEMENT UNDER CONDITIONS WHICH REDUCE SAID COBALT (III) TO COBALT (II) AND IN TURN OIDIZE SAID COLORDEVELOPING AGENT TO PROVIDE AN INCREASE IN DYE DENSITY WITH DYE PRODUCED FROM SAID COUPLER IN THE AREAS CORRESPONDING TO THE IMAGEWISE DISTRIBUTION OF SAID METALLIC SILER, THE IMPROVEMENT COMPRISING INCLUDING IN SAID AMPLIFIER COMPOSITION AN FE(III) CHELATE OF AN AMINOCARBOXYLIC ACID.

Nov. 5, 1974 M. D. PUROL ET AL PROCESS FOR DEVELOPING PHOTOGRAPHIC ELEMENTS Filed May 21, 1973 FIG.

EXAMPLE IA (CONTROL) EXAMPLE [5 (CONTROL) r r I I I I I I I I I sTEPw/sEEXP0sL/RE EXAMPLE II A I I I I I I I I I l8/7/6/5/4/3/2/l/0987b STEPW/SE EXPOSURE EXAMPLE .ZZ'B

I I I I I I I I I T I I .STEPW/SE EXPOSURE United States Patent 3,846,130 PROCESS FOR DEVELOPING PHOTOGRAPHIC ELEMENTS Michael Dennis Purol and Richard Joseph Malloy,

Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, NY.

Filed May 21, 1973, Ser. No. 361,925 Int. Cl. G03c 1/40, 7/00 US. Cl. 96--22 16 Claims ABSTRACT OF THE DISCLGSURE Improved processes are disclosed for providng an image record in a photographic element which comprises a support and at least one layer thereon containing a silver halide emulsion which has associated therewith an image dye-providing color coupler. Generally, the process comprises contacting a photographic element containing a silver halide and an imagewise distribution of metallic silver with a color-developing agent and then contacting the developed photographic element with an amplifier composition which contains a cobalt(Il'I) complex and an Fe(HI) chelate of an aminocarboxylic acid.

This invention relates to a process for developing photographic elements which comprise layer units containing imagewise-exposed silver halide having associated therewith a photographic color coupler. In one aspect, this invention relates to a process for developing a visible image record in photographic elements which comprise color-providing layer units containing a low silver coverage. In another aspect, this invention relates to a continuous process for developing imagewise-exposed photographic elements which comprise at least two colorproviding layer units.

It is known in the art to process photographic elements comprising silver halide emulsions and photographic color couplers wherein said element is contacted with an aromatic primary amino silver halide developing agent to form silver and dye. References such as US. Pats. 2,750,292 by Dippel et al. issued June 12, 1956, and 2,173,739 by Weber issued Sept. 19, 1939*, disclose processes for intensifying an image formed by a lightsensitive metal salt by treating the imagewise-exposed element with a color-developing agent and a photographic color coupler in the presence of developable silver halide or with a physical developing agent to form an image dye in the area of development. More recently, British Pat. 1,268,126 also discloses a process of intensifying a silver image by treating a developed silver image with solutions containing peroxy compounds and color developers.

However, several of the methods available in the art do not appear to be practical on a commercial basis due to several problems inherent in the system, including instability of the solutions used to intensify the image record recorded by the light-sensitive metal salt. Where the silver is bleached and redevelopment takes place with a color developer and a coupler, the bleaching step is quite critical as the developable silver sites can be lost where bleaching has completely converted a silver grain to silver halide and, moreover, solutions containing both color-developing agent and color coupler are prone to formation of dye in the bath through aerial oxidation of the developer, etc., causing eye contamination, and also these systems are generally limited to one-color systerns. Where a physical developing agent is used in combination with a color coupler and a color-developing agent, the processing baths are often autocatalytic since the reaction products of the redox reaction with the physical developer provide a catalyst for more redox reactions.

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New processes for developing and amplifying an image record recorded in a light-sensitive metal salt are disclosed in Belgian Pats. 784,471, 784,472 and 784,473, incorporated herein by reference. In one embodiment, the process disclosed in these patents. relates to image formation in photographic elements comprising colorproviding layer units containing a silver halide emulsion having associated therewith a color coupler. In the proc ess, the photographic element is contacted with a photographic color-developing agent and a metal complex, such as a cobalt(III) having a coordination number of 6, until the desired dye density is obtained. The cobalt complex is apparently reduced to cobalt(II), which is not a catalyst for further redox reaction, in the presence of silver, and the color developer is oxidized whereby it can react with the color coupler in each respective layer unit to form the desired image dye. Certain preferred photographic elements which can be process by this procedure are described in Bissonette, U.S. Ser. No. 256,072 filed May 23, 1972, incorporated herein by reference.

These patents also disclose a process of producing image dye in an imagewise-exposed photographic element having a support and at least one layer thereon containing a silver halide emulsion having associated therewith an image dye-providing color coupler wherein said process comprises (1) development of said imagewise-exposed photographic element with a. silver halide developing agent to produce an imagewise distribtuion of metallic silver in imbibition of a color-developing agent in said photographic element, and then (2) contacting said photographic element which contains silver halide and said imagewise distribution of metallic silver with an amplifier composition which represses substantially additional net silver development, wherein said amplifier composition contains a cobalt(HI) metal complex having a coordination number of 6 and said amplifier composition is maintained in said photographic element under conditions which reduce cobalt(III) to cobalt(II), which in turn oxidizes said color-developing agent whereby additional image dye is provided from said image dye-providing color coupler and said oxidized color-developing agent.

The amplifier composition acts essentially as a stop bath so far as further production. of catalytic silver surface is concerned. Further H and D curve shape changes due to continued development are therefore minimized. However, in some continuous deep tank-machine developing processes, it has been observed that carry-over of color-developing agent from the developer bath to the amplifier bath has caused some sensitometric fluctuations and changes in the H and D curve shape. These fluctuations are presumably due to the fact that excess colordeveloping agent in the amplifier bath reduces the diffusion rate of color developer from the photographic element. This causes a gradual contrast increase, thereby creating a problem of precise sensitometric control.

This invention relates to an improved process of producing image dye in an imagewise-exposed photographic element having a support and at least one layer thereon containing a silver halide emulsion having associated therewith an image dye-producing color coupler wherein said process comprises (1) development of said imagewise-exposed photographic element with a silver halide developing agent to produce an imagewise distribution of metallic silver and imbibition of a color-developing agent in said photographic element, and then (2) contacting said photographic element with an amplifier composition which represses substantially additional net silver development, wherein said amplifier composition contains an Fe(III) chelate of an aminocarboxylic acid and a cobalt(III) metal complex having a coordination number of 6.

In one highly preferred embodiment, an image dye is produced in an imagewise-exposed photographic element having a support and at least one layer thereon containing a silver halide emulsion having associated therewith an image dye-providing color coupler. The imagewise-exposed photographic element is developed in the presence of a silver halide color-developing agent. This produces an imagewise distribution of metallic silver and imbibition of a color-developing agent in the photographic element. The developed photographic element which contains silver halide and the imagewise distribution of metallic silver is then contacted with an amplifier composition which represses substantially additional net silver development. The amplifier composition contains a Fe(III) chelate of an aminocarboxylic acid which selectively oxidizes any excess developing agent which may have been carried to the amplifier bath. The chelate selected should have no efiect on other amplifier addenda.

In certain preferred embodiments, chelates used in accordance with this invention are of the following formula:

wherein:

L is a group containing from 1-20 carbon atoms and can be an alkylene group, a substituted alkylene group, a cycloalkylene group, a substituted cycloalkylene group, and the like;

x is 0, 1 or 2; R can be an alkylene group of 1-5 carbon atoms or a substituted alkylene group of 1-5 carbon atoms; and

R and R which can be the same or different, each can be a hydrogen atom; an alkyl group or a substituted alkyl group of 1-10 carbon atoms, being substituted by hydroxyl, halogen, alkoxy, carbamoyl, amino, substituted amino, epoxy, carboxyl, sulfo, phospheno, mercapto, alkylmercapto, alkoxycarbonyl, and a nitrogen-containing heterocyclic ring; an aralkyl group; a substituted aralkyl group, being substituted by hydroxyl, halogen, alkyl, alkoxy, nitro, carboxyl and sulfo; an aryl group; or a substituted aryl group, being substituted by hydroxyl, halogen, alkyl, alkoxy, nitro, carboxyl, sulfo, and the like. The following is a partial list of aminocarboxylic acids according to the above formula: (1) ethylenediamine,N,N,N,N-tetraacetic acid (2) 1,2-propylenediamine,N,N,N,N-tetraacetic acid (3) ethylenediamine,N,N,N,N-tetrapropionic acid (4) N- (2-hydroxyethyl ethylenediamine,N,N,N-

triacetic acid 5) N- Z-hydroxypropyl ethylenediamine,N,N,N-

triacetic acid (6) N-(2,3-dihydroxypropyl)ethylenediamine,N,N,N-

triacetic acid (7) N,N-di Z-hydroxyethyl) ethylenediamine,N,N.

diacetic acid (8) diethylenetriamine,N,N,N,N,N-pentaacetic acid (9) nitrilo triacetic acid (10) ethylenediamine,N,N-di-(o-hydroxyphenyl acetic acid) (11) di(2-hydroxyethyl)amino acetic acid (12) 2-hydroxyethylamino diacetic acid (13) 1,2diaminocyclohexane,N,N,N,N-tetraacetic acid (14) 2,S-dihydroxypropylamino diacetic acid (15) ethylene glycol bis(2-aminoethyl)N,N,N,N-

tetraacetic acid (16) N,N-di[ 3-di(2-hydroxyethyl amino-2-hydroxypropyl]ethylenediamine,N,N-diacetic acid 17) N- (2-hydroxyethyl)-N-(at-pyridinomethyl) ethylenediamine,N,N-diacetic acid (18) N-(Z-hydroxyethyl)-Nphosphonomethylethylenediamine,N,N-diacetic acid (19) N- (2,3-dihydroxypropyl) -N-(2-sulfoethyl) ethylenediamine,N,N-diacetic acid Cit (20) N,N-di(2-hydroxyethyl)ethylenetriamine,

N,N,N-triacetic acid (21) N-(Z-mercaptol-carboxyethyl) -N-(2-hydroxyethyl)ethylenediamine,N,N-diacetic acid (22) N-(3,S-dichloro-4-hydroxybenzyl)-N-(2-hydroxyethyl) ethylenediamine,N,N-diacetic acid (23) 2-hydroxypropylenediamine,N,N,N,N-tetraacetic acid (24) 1,3-diamino-2-proponal tetraacetic acid (25) ethyleneglycol-bis-(aminoethylether) tetraacetic acid (26) trans-1,2-diaminocyclohexane tetraacetic acid In certain preferred embodiments, the Fe(III) complex is ferric ethylenediamine tetraacetic acid or ferric nitrilotriacetic acid.

The ferric chelates used in this invention can be prepared by processes well-known to those skilled in the art, such as by reacting a salt of the ferric ion with the salt of a weak or strong mineral or organic acid with a chelating agent and then isolating the product.

The photographic elements processed as above can, of course, be bleached, fixed, washed, etc., in the normal manner after contact with the amplifier. Generally, this process also provides highly improved stability of development compositions and amplifying compositions and is especially suited to continuous processing of color photographic elements. The process is especially advantageous in processing multicolor photographic elements since stability in processing solutions is highly improved, allowing reproducible results over long periods of operating time.

In one preferred embodiment, the amplifier solution contains a sufiicient quantity of a development restrainer or combination of development restrainers to repress substantially any further net silver development. The development restrainers may be water-soluble bromide compounds such as KBr, etc., or heterocyclic compounds such as tetrazoles, azaindines and triazoles which are free from mercapto or ionic iodide groups. Development restrainers as a class of compounds are known in the art, as mentioned in US. Pat. 3,458,317. Development restrainers which have ionic iodide groups or mercapto groups appear to retard the catalytic effect of silver. Typical preferred development restrainers include high levels of KBr, such as 2 to 40 g./l., methyl benzotriazole, benzotriazole, 3- methyl-1,3-benzothiazolium bromide, 5-nitrobenzimidazole, decamethylene bis(benzothiazolium bromide) and the like. Other useful organic development restrainers include the sodium salt of 4 hydorxy 6 methyl 1,3,3a,- 7 tetrazaindene, the sodium salt of -4 hydroxy 6 methyl 2 methylmercapto 1,3,3a,7 tetrazaindene, 4,5 dihydro 1,4 diphenyl 3,5 phenylamino 1,2,4- triazole and the like. The heterocyclic development restrainers are generally incorporated in the amplifier at concentrations of .01 to 2.0 g./ 1. In certain embodiments, the heterocyclic groups containing sulfur substitution can be used as development restrainers where the compound as used in the amplifier remains in its thione form rather than in the thiol or mercapto forms. In highly preferred embodiments, a combination of an alkali metal bromide and an organic development restrainer are present in the amplifier composition.

The amplifying baths of this invention preferably contain only low amounts of or are substantially free from silver halide solvents. If high amounts of solvents are present, there is very little noticeable amplification effect in the bath. Therefore, the amplifying baths generally comprise less than 30% by weight of the amount of a silver halide solvent which would be necessary to fix a silver halide emulsion. The fixing processes are well-known in the art, for example, as disclosed in US. Pat. 3,615,508.

As used herein, the terms photographic color coupler and image dye-providing color coupler include any compound which reacts (or couples) with the oxidation products of primary aromatic amino developing agent on photographic development to form an image dye and are preferably nondiffusible in a hydrophilic colloid binder, useful for photographic silver halide, and also those couplers which provide useful image dyes when reacted with oxidized primary aromatic amino developing agents such as by a coupler-release mechanism. The couplers can form diffusible or nondiffusible dyes. Typical useful color couplers include phenolic, S-pyrazolone and open-chain ketomethylene couplers. Specific cyan, magenta and yellow dye-forming couplers which can be employed in the practice of this invention are described in U.S. Pat. 3,046,- 129, column 15, line 45, through column 18, line 51, which disclosure is incorporated herein by reference. Such color couplers can be dispersed in any convenient manner, such as by using the solvents and the techniques described by U.S. Pat. 2,322,027 or 2,801,171. When coupler solvents are employed, the most useful weight ratios of color coupler to coupler solvent range from about 1:3 to 1:0.1. Useful couplers include Fischer-type incorporated couplers such as those described in U.S. Pat. 1,055,155 and particularly nondifi'usible Fischer-type couplers containing branch carbon chains, e.g., those referred to in the references cited in U.S. Pat. 2,376,679, column 2, lines 50-60. Particularly useful in the practice of this invention are the nondiffusible color couplers which form nondiffusible dyes.

In certain preferred embodiments, the incorporated couplers in the layer units of this invention are water-insoluble color couplers which are incorporated in a coupler solvent which is preferably a moderately polar solvent. Typical useful solvents include tri-a-cresyl phosphate, di-nbutyl phthalate, diethyl lauramide, 2,4 diaryphenol, liquid dye stabilizers as described in an article entitled Improved Photographic Dye Image Stabilizer-Solvent, Product Licensing Index, Vol. 83, March 1971, and the like. The coupler solvents in the elements appear to aid the imbibition of color developer when it is carried into an amplifier bath via the element.

The photographic elements processed in accordance with this invention generally comprise a light-sensitive silver halide emulsion wherein the halide is generally less than 6 mole percent iodide and preferably less than 3 percent iodide and, in some highly preferred embodiments, is less than 0.25 percent iodide. If iodide is near the surface of the emulsion grains, it can build up in the solutions at a high level during development and amplification and affect dye production in the amplification step. Therefore, high amounts of iodide in the emulsion are generally avoided, especially when the element is to be processed in a continuous-process, deep-tank apparatus.

The term nondilfusible used herein as applied to cou plers and products derived from couplers has the meaning commonly applied to the term in color photography and denotes materials which for all practical purposes do not migrate nor wander through photographic hydrophilic colloid layers, such as gelatin, particularly during pro..- essing in aqueous alkaline solutions. The same meaning is attached to the term immobile. The terms diffusible and mobile have the converse meaning.

The photographic elements processed in accordance with this invention, as defined above, comprise a support having thereon image dye-providing layer units. A multicolor photographic element comprises at least two of said image dye-providing layer units which each record light primarily in different regions of the light spectrum. The layer unit comprises a light-sensitive silver salt which is generally spectrally sensitized to a specific region of the light spectrum and has associated therewith a photo graphic color coupler. In certain embodiments, the colorproviding layer units are eifectively isolated from other layer units by barrier layers, spacer layers, layers containing scavengers for oxidized developer, and the like, to prevent any substantial color contamination between the image dye-providing layer units. The effective isolation of the layer units is known in the art and is utilized to prevent color contamination in many commercial color products.

The photographic elements processed in accordance with this invention preferably comprise a support having thereon at least one image dye-providing layer unit and preferably at least two image dye-providing layer units containing a light-sensitive silver salt, preferably silver halide, having associated therewith a stoichiometric excess of coupler of at least 40% and at least preferably 70%. The equivalency of color couplers is known in the art; for example, the 4-equivalent couplers require 4 moles of oxidized color developer, which in turn requires development of 4 moles of silver, to produce 1 mole of dye. Thus, for a stoichiometric reaction with silver halide l-equivalent weight of this coupler will be 0.25 mole. In accordance with this embodiment, the color image-providing unit comprises at least a 40% excess of the equivalent weight of image dye-providing color coupler required to react with the silver and preferably a 70% excess of said coupler based on effective silver. In certain highly preferred embodiments, the photographic color couplers are employed in the image dye-providing layer units at a concentration of at least 3 times, such as from 3 to 20 times, the weight of the silver in the silver halide emulsion, or at a stoichiometric excess of at least 110% based on effective silver in said layer unit. Advantageously, the coupler is present in an amount sufficient to give a density of at least 1.7 and preferably at least 2.0 when coated on a paper support and preferably at least 3.0 when coated on a transparent film support. Generally, the coupler is present in said layer units in at least l 1O moles/ft Preferably, the difference between the maximum density and the minimum density (which can comprise unbleached silver) is at least .6 and preferably at least 1.0. Preferably, the photographic elements prepared in accordance with this invention are those described in the above Bissonette application U.S. Ser. No. 256,077.

Advantageously, the photographic color couplers utilized are selected so that they will give a good neutral. Preferably, the cyan dye formed has its major absorption between about 600 and 700 nm., the magenta dye has its major absorption between about 500 and 600 nm., and the yellow dye has its major absorption between about 400 and 500 nm.

Generally, each of the color-providing layer units of the photographic elements contains a light-sensitive silver halide. In one preferred embodiment, the color-providing layer units comprise a silver salt at a concentration of up to 30 mg. silver/ft? However, while the silver halide is preferably present at concentrations based on silver of less than 30 mg./ft. it is possible to coat emulsions at higher silver coverages within this embodiment as long as no more than 30 mg./ft. of silver develops; for example, such emulsions may contain silver halide grains which are relatively light-insensitive or may contain developer restrainers such as development inhibitor-releasing coupplers, and still provide a photographic element which is advantageously used in the various processes as described herein to produce improved image records. In some instances, relatively light-insensitive silver halide grains or development restrainers are desirable to enable one to obtain more uniform coating coverage with less precise coating equipment, as well as for other reasons. Thus, highly preferred photographic elements processed according to this invention contain at least two color-providing layer units, each containing a silver halide emulsion, defined in terms of effective coverage and developability as one which, when it is fully exposed and processed for about 1 min. at F. in the color developer as described in Example 1, will provide less than 30 mg. of metallic silver/ft. and preferably less than 15 mg./ ft. It is understood that the term effective silver refers to that amount of silver which is produced in this test and that ratios of coupler to silver are based on effective silver which is produced by this type of development when so specified herein. In most instances, the quantity of ef* fective silver as silver halide in the undeveloped, unexposed photographic element will be quite similar to quantity of total silver present as silver halide. The fully exposed layer containing silver halide emulsion is one which is exposed to D as is well-known in the art, for example, by exposure to a SOO-watt, 3000 K. lamp for about 10 sec. (total exposure at the film plane=11.3 10 crgs/cm.

The photographic elements processed in accordance with this invention generally can contain negative silver halide emulsions, direct-positive silver halide emulsions, silver halide emulsions designed for processing in reversal processes, and the like. It is understood, of course, that with negative emulsions the catalytic metallic silver de velopment will be in the exposed areas, whereas with direct-positive emulsions the catalytic metallic silver will be formed in the unexposed areas.

The amplifier compositions of this invention include a cobalt(III) metal complex. Such complexes feature a molecule having a cobalt atom or ion. This cobalt atom or ion is surrounded by groups of atoms, ions, or other molecules, which are generically referred to as ligands. The cobalt atom or ion in the center of these complexes is a Lewis acid; the ligands are Lewis bases. Werner complexes are well-known examples of such complexes. The useful cobalt salts are typically capable of existing in at least two valent states. In a preferred aspect of the invention, the cobalt complexes are those referred to by American chemists as inert and by European chemists as robust. Particularly useful are complexes of a cobalt ion with a ligand which, when a test sample thereof is dissolved at .1 molar concentration at 20 C. in an inert solvent solution also containing .1 molar concentration of a tagged ligand of the same species which is uncoordinated, exhibits essentially no exchange of uncoordinated and coordinated ligands for at least 1 min., and preferably for at least several hours, such as up to 5 hrs. or more. This test is advantageously conducted under the pH conditions which will be utilized in the practice of the invention. In silver halide photography, this generally will be a pH of over about 8. Many cobalt metal complexes useful in this invention show essentially no exchange of uncoordinated and coordinated ligands for several days. The definition of inert metal complexes and the method of measuring ligand exchange using metal radioactive isotopes to tag ligands are well-known in the art; see, for example, Taube, Chem. Rev., Vol. 50, p. 69 (1952), and Basolo and Pearson, Mechanisms of Inorganic Reactions, A Study of Metal Complexes and Solutions, 2nd Edition, 1967, published by John Wiley and Sons, p. 141. Further details on measurement of ligand exchange appear in articles by Adamson et al., J. Am. Chem. Soc., Vol. 73, p. 4789 (1951). The inert metal complexes should be contractcd with labile complexes which, when tested by the method described above, have a reaction half-life generally less than 1 min. Metal chelates are a special type of metal complex in which the same ligand (or molecule) is attached to the central metal ion at two or more different ponits. The metal chelates generally exhibit somewhat slower ligand exchange than nonchelated complexes. Labile-type chelates may have a half-life of several seconds or perhaps slightly longer. Generally, the oxidizing agents employed are not reduced to a zero valent metal during the redox reaction of the invention.

A wide variety of ligands can be used with a cobalt ion to form suitable cobalt complexes. Nearly all Lewis bases (i.e., substances having an unshared pair of elec trons) can be ligands in cobalt complexes. Some typical useful ligands include the halides, e.g., chloride, bromide, fluoride, nitrite, water, amino, etc., as well as such common ligands as those referred to on p. 44 of Basolo et al., supra. The lability of a complex is influenced by the nature of the ligands selected in forming said complex.

Particularly useful cobalt complexes have a coordination number of 6 and have a ligand selected from the group consisting of ethylenediamine(en), propylenediamine (tn) diethylenetriamine dien) triethylenetetraamine(trien), amine(NH nitrate, nitrite, azide, chloride, thiocyanate, isothiocyanate, water and carbonate. The preferred cobalt complexes comprise 1) at least 2 ethylenediamine ligands or (2) at least 5 amine ligands or (3) 1 triethylenetetraamine ligand. Especially useful are the cobalt hexammine salts (e.g., the chloride, bromide, sulfite, sulfate, perchlorate, nitrite and acetate salts). Some other specific highly useful cobalt complexes include those having one of the following formulas:

[Co(tn) (en)X and [Co(tn)(en) ]X, wherein X represents one or more anions determined by the charge neutralization rule.

With many complexes, such as cobalt hexammine, the anions selected can substantially affect the reducibility of the complex. The following ions are listed in the order of those which give increasing stability to cobalt hexammine complexes: bromide, chloride, nitrite, perchlorate, acetate, carbonate, sulfite, sulfate. Other ions will also affect the reducibility of the complex. These ions should, therefore, be chosen to provide complexes exhibiting the desired degree of reducibility. Some other useful anions include nitrate, thiocyanate, dithionate and hydroxide. Generally, metal-ion complexes having a net positive charge are preferred.

Numerous color-developing agents can be imbibed in the photographic element in accordance with the present invention. The color-developing agents utilized herein undergo redox reaction with the oxidizing agent at a catalytic surface. Especially preferred color-developing agents are those which reduce silver halide to metallic silver, such as those which are capable of developing imagewise-exposed light-sensitive photographic silver halide. Typical preferred color-developing agents are aromatic primary amino color-developing agents as p-aminophenols (which form particularly stable redox combinations with certain complexes, e.g., [Co(en) Cl or pphenylenediamines. Useful color-developing agents include 3-acetamido-4-amino-N,N-diethylaniline, p-amino-N-ethyl- N-B-hydroxyethylaniline sulfate, N,N-diethyl-p-phenylenediamine, 2 amino S-diethylaminotoluene, N-ethyl-N-B- methanesulfonamidoethyl 3 methyl-4-aminoaniline, 4 amino-N-ethyl-B-methyl-N-(B-sulfoethyDaniline, 4-amino- N-butyl-Ne-sulfobutylaniline, 4 amino-N,N-diethyl-3-npropylaniline hydrochloride and the like. See Bent et al., JACS, Vol. 73, pp. 31003125 (1951), and Mees and James, The Theory of the Photographic Process, 3rd Edition, 1966, published by MacMillan Co., New York, pp. 278-311, for further typical, useful developing agents. It will be appreciated that many of the subject color-developing agents are most effective at high pH, such as pH from about 8 to 13.

In one highly preferred embodiment, aromatic primary amino color-developing agents which provide good results in the process of this invention are 4-amino-N,N-diethylaniline hydrochloride, 4 amino-3-methyl-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N-ethyl-N-[i-(methanesulfonamido)ethylaniline sulfate hydrate, 4 amino-3- methyl-N-ethyl-N-,B-hydroxyethylaniline sulfate, 4-amino- 3 dimethylamino-N,N-diethylaniline sulfate hydrate, 4- amino-3-methoxy-N-ethyl-N-B-hydroxyethylaniline hydrochloride, 4 amino-N-ethyl-N-(Z-methoxyethyl)-m-toluidine di-paratoluene sulfonate, and 4-amino-3-[3-(methanesulfonamido)-ethyl-N,N-diethylaniline dihydrochloride.

The term color developer as used herein generally refers to those silver halide developing agents which, after oxidation, couple with a photographic color coupler to form an addition compound such as an image dye. Generally, these compounds contain a primary amino group (NH and they are preferably aromatic primary amino compounds where the primary amino group is a substituent on the aromatic ring.

The black-and-white silver halide developers, as referred to herein, generally refer to those developers "which do not couple with photographic color couplers to form useful image dyes. The black-and-white silver developers can be effectively used in some instances in the formation or development of the metallic silver in the photographic element. Typical useful developers of this type include hydroquinones, catechols, 3-pyrazolidones such as l-phenyl- 3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, 1- phenyl-4-methyl-3-pyrazolidone and the like, l-, d-, or isoascorbic acid, reductones, N-methyl-p-aminophenyls and the like.

The amplifier bath can generally comprise any liquid as a carrier medium, but the liquid is preferably predominantly water. The bath generally comprises from about 0.2 to about 20 g./l. of the transition metal-ion complex which preferably is maintained at between about 1 to about 15 g./l. However, generally higher concentrations of cobalt complexes can be used in preferred amplifier baths of this invention without adverse sensitometric effects, compared with color-developing solutions which contain the cobalt complexes which contain sufficient colordeveloping agent to develop substantial amounts of silver halide rapidly.

The amplifier baths of this invention are generally maintained with an Fe(III) chelate concentration of at least 1 10- g./l. up to the solubility limit of the particular Fe(III) chelate. In highly preferred embodiments, the amplifier contains from 1 10 g./l. up to the solubility limit of the Fe(III) chelate at the pH and temperatures of operation.

The amplifier bath can also contain solubilizing agents for the oxidized developing agents. Typical useful solubilizing agents are the alkali metal sulfites such as sodium sulfite. The sulfites are generally used in the solution at a stoichiometric concentration or a slight excess, such as up to a 30% excess, based on the color developer present. The sulfites generally prevent some of the adverseeffects encountered with an oxidized color developer, such a scumming, tar formation, etc.

The amplifier bath generally contains a development restrainer and preferably contains enough development restrainer to repress any further silver formation. Thus, the sensitometric changes associated with the development of silver are avoided. Moreover, this feature enables one to use various grain sizes in various layers of a multicolor element to obtain a balanced photographic element and simultaneously provide substantially uniform color formation in each layer, whereby balanced color can be obtained at several densities by inspection.

The organic development restrainers (i.e., other than the inorganic development restrainers such as the alkali metal bromides) mentioned previously can be used in the bath in combination with the inorganic development restrainers or alone, but are preferably used in combination with alkali metal bromides. Generally, the organic development restrainers are used in concentrations of from to 2 g. and preferably from .01 to 1 g./l.

The amplifier bath is generally operated in a pH range of from 6 to 14 and preferably at pH ranges of 8 to 12.

The amplifying baths contain only small amounts of Or are substantially free from silver halide solvents such as sodium thiosulfate, thiocyanates, thioethers and the like. While bromide ions are often desirable in small amounts of about 2 to 40 g./l. of amplifying solution to repress development, high concentrations such as above 200 g./l. could function to bleach silver halide layers and, likewise, defeat the primary amplification step. In certain embodiments, it is also desirable to maintain the ammonia in the amplifier at less than 10 g./l. since high ammonia 10 concentrations can act as a silver halide solvent, thus allowing bleaching of the silver'image.

The term silver halide solvents generally refers to compounds and concentration levels of those compounds which, when employed in an aqueous solution (60 C), are capable of dissolving more than ten times the amount (by weight) of silver chloride than that which can be dissolved by water at 60 C.

The concentration of a solvent necessary to fix a silver halide layer is understood to mean that concentration of solvent in a liouid bath which will remove substantially all silver bromide from a photographic element containin a single silver bromide gelatin emulsion layer coated at 30 m silver/ft. in 1 /2 min. at 105 F. maintained at a pH ra e within 4.012.0.

The amplifier bath can be op rated over a wide range of temperatures depending on the effect desired. Gen ral the am lifier bath is much more stable than amplifier baths reviouslv used and therefore is preferahlv u ed in nrocesses where it is onerated at temperatures above F.. and more nreferablv above F.. to decrease the reside ce time of a photographic element in the bath, th s spe din u the process.

The developin baths and amplifier solutions of this inven ion preferably contain a coupling accelerator which can be an alcohol. including aromatic alcohols. which appears to increase dve Vields. Tvpical useful aromatic a oho s include benv l alcohol. benzvloxvethanol. cvclnhexanol. nentvl alcohol. phenoxvethvl alcohol, phenylethvl alcohol and the like. Preferably th alcohol is used in the resnec ive baths at concentrat ons of no to 0 g /l. and nreferahlv from about 2 g. to 20 /l. Cfillnlifl" acce er tors are known in the art. for exam le. the alcohols disc osed in US. Pa s. 2.304.92 2.950.920 and the like.

Preferablv. the process is carried out in a unidirectional n ocessing enuinment where the element leaves a bath in the same relative direction with respect to the plane of the e ement as it enters the bath. In certain nr ferred em odiments. a continuous web of the photo raphic material is rocessed in unidirectional continuous-process ng equipment.

Several features of the present process are apnarent from FIGS. 1-4 ac ompanying this application. FIGS. 1 and 2 are H and T) curves of the control image records of Example 1. F GQ. 3 and 4 are H and D curves of the image reco ds of Example 2. The desi nations B. G and R refer to the curves roduced b he blue-sensitive la r unit. the reen-sens tive layer unit and the red-sensitive lav r unit respectivelv.

The invention can be further illustrated by the following examples.

EXAMPLE l-A (CONTROL) To serve as a control, a photographic element is prepared by coating the following layers in order on a paper support:

(1) Layer containing a blue-sensitive silver halide emulsion at 16 mg./ft. based on silver, gelatin at 122 mg./ft. the yellow image dye-providing coupler a-pivalyl-4-(4 benzyloxyphenylsulfonyl)phenoxy 2 chloro-5-[a-2,4- di-tert-amylphenoxy)butyramido]acetanilide at 60 mg./ ft. dissolved in di-n-butyl phthalate coupler solvent at 15 mg./ft.

(2) Gelatin interlayer at 100 mg /ft. and the scavenger for oxidized developer di-tert-octyl hydroquinoue at 5 mg./ft.

(3) Layer containing a green-sensitive silver halide emulsion at 10 mg./ft. based on silver, gelatin at 132 mg./ft. and the magenta dye providing color coupler 1 (2,4,6 trichlorophenyl)-3-{5-[a(3-tert-butyl-4-hyd1oxyphenoxy)tetradecaneamido] 2 chloroanilino}-5- pyrazolone at 25 mg./ft. dissolved in tri-cresyl phosphate coupler solvent at 12.5 mg./ft.

(4) Gelatin interlayer containing mg./ft. and ditert-octyl hydroquinone at 4.5 mg./ft.

Layer containing a red-sensitive silver halide emulsion at 6 mg./ft. based on silver, gelatin at 90 mg./ft. and the cyan dye image-providing coupler 2-[a-(2,4-ditert-amylphenoxy)butyramido] 4,6 dichloro-S-methyL phenol at 35 mg./ft. dissolved in di-n-butyl phthalate coupler solvent at 17.5 mg./ft.

(6) Gelatin overlayer at 100 mg./ft. of gelatin.

Samples of the coated paper support are sensitometrically exposed to a multicolor, graduated-density test object and then processed in the following sequence:

Color-develop 1.0 min. (40 C.). Amplify 1.5 min. (40C.). Bleach-fix 1.0 min. (40 C.). Wash 1.5 min. (26 C.). Dry.

The respective processing baths have the following compositions:

COLOR DEVELOPER Benzyl alcohol ml K 80 g 4 KBr g 0.4 Hydroxylamine sllfate g 2 4-amino-N-ethyl-N- (2 methoxyethyl) -m-toluidine diparatoluene sulfonate g 7.5 K CO g 30 Diaminopropanol tetraacetic acid g 5 Water to 1 liter. pH 10.1.

AMPLIFIER v g KBr g 2 Benzyl alcohol ml 15 K CO g 7.5 K 80 g 2.0 Diaminopropanol tetraacetic acid -g 10.0 Water to 1 liter. pH 10.1.

BLEACH-FIX Diaminopropanol tetraacetic acid g 3 Acetic acid ml (NH4)2S2'O3 ml Na2SO3 g [C0(NH3)6]C13 g 3 Water to 1 liter. pH 4.5.

The processed sample is sensitometrically evaluated by recording the H and D curves of the developed dye im- 1 ages; the curves are illustrated in FIG. 1.

EXAMPLE 1-B (CONTROL) An additional sample of the photographic element of Example 1-A is processed with the provision that the amplifier bath also contains 2.0 g./l. of 4arnino-N-ethyl- N- Z-methoxyethyl -m-toluidine di-paratoluenesulfonate to stimulate buildup of color developer in the amplifier bath. The processed sample is sensitometrically evaluated by recording the H and D curves which are illustrated in FIG. 2. A comparison of the sets of curves of FIGS. 1 and 2 shows the increased image contrast and speed caused by the added color developing agent.

EXAMPLE 2-A Another sample of the photographic element of Example 1-A is processed as in Example 1 but with the amplifier bath also containing 5 ml./l. of a 1.56 molar solution of ferric ethylenediamine tetraacetic acid. The results of processing are illustrated in FIG. 3.

EXAMPLE 2-B A repeat of the procedure of Example 1-B with the amplifier bath also containing 2.0 g./l. of the color-developing agent of Example l-A produces the results illustrated in FIG. 4. A comparison of the sets of curves in FIGS. 3 and 4 shows the effectiveness of ferric ethylenediamine tetraacetic acid in maintaining image contrast and speed.

EXAMPLE 3 Additional samples of the photographic element of Example l-A are processed as in Example 1 with the addition of ferric nitrilotriacetic acid, ferris trans-1,2-diaminocyclohexane tctraacetic acid monohydrate, ferric ethyleneglycol-bis-(aminoethyl ether) tetraacetic acid, and ferric 1,3-diamino-2-propanol tetraacetic acid to separate amplifier baths. The ferric complexes are used at levels close to their solubility limits. Similar improvements in maintaining image contrast and speed in the image records are obtained with these compounds as compared with ferric ethylenediamine tetraacetic acid as used in Example 2.

As can be observed from the foregoing examples, the changes in D min., D max., and contrast of continuously processed photographic elements are minimized by the addition to the bath of certain Fe(III) chelates.

EXAMPLE 4-A An exposed sample of the photographic element of Example 1 is processed in the following sequences:

Color-develop 1.0 min. (40 C.) Amplify 1.5 min. (40 C.) Bleach-fix 1.0 min. (40 C.) Wash 1.5 min. (26 C.) Dry.

The respective processing baths have the following compositions:

COLOR DEVELOPER Benzyl alcohol ml 15 K g 4 KBr g 0.4 Hydroxylamine sulfate g 2 4 amino-N-ethyl-N-(2-methovyethyl)-m toluidine di-paratoluene sulfonate g 7.5 K CO g 30 Nitrilotriacetic acid g 6.5 Water to 1 liter. pH 10.1.

AMPLIFIER Benzyl alcohol ml 0.5 [Co(NH ]Cl g 10 KBr g 2 K2003 g 7.5 K2503 g 2-0 Nitrilotriacetic acid. g 13.0 Water to 1 liter. pH 10.1.

BLEACH-FIX Diaminopropanol tetraacetic acid g 3 Acetic acid ml 20 60% (NH S O ml Na SO g 15 [C0(NH3)6]C13 --g- 3 Water to 1 liter. pH 4.5.

A processed sample is evaluated by recording the H and D curves of the developed yellow, magenta and cyan dye images.

Another sample of the same photographic element is processed by the identical procedure with the exception that 7.0)(10 moles/liter of ferric nitrilotriacetic acid complex in the form of NH Fe(III) nitrilotriacetic acid are added to the amplifier. The H and D curves of the respective dye images in the sample are recorded.

Upon comparison of the samples processed by the above procedures, it is apparent that the addition of the ferric 13' nitrilotriacetic acid complex does not produce any noticeable detrimental eifects in the densitometric results of the processed samples.

EXAMPLE 4-B A large volume of the photographic element described in Example 1 is processed in a continuous-run operation wherein the solutions and residence time in each solution are the same as described in Example 4-A. In one continuous run of 300 min., a control operation is run where the amplifier has no added NH Fe(III) nitrilotriacetic acid, whereas in another run the amplifier (Amplifier 4-B) contains 1.16 moles/liter of NH Fe(III) nitrilotriacetic acid.

During each continuous-processing cycle, both amplifier solutions are analyzed at 30-min. intervals for excess color-developing agent carried over from the developing bath. The results are reported in g./l. of color developer present and are tabulated below:

Time of sampling .ll. of color developer Control Amplifier 4,-B-

It is apparent that the ferric nitrilotriacetic acid is eifective in preventing an excessive accumulation of color-developing agent in the amplifier bath.

Samples of the photographic element produced in each process are taken at 30-min. intervals during the process and the H and D curves are recorded for the respective samples. A comparison of the H and D curves indicates that there is a gradual density buildup in the image record of the elements produced in the control amplifier, whereas the density of the image record in the elements produced in the amplifier containing the ferric nitrilotriacetic acid is substantially the same in the records produced after 2.0 hr. of continuous use of the amplifier as in the initially produced image records.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be elfected within the spirit and scope of the invention.

We claim:

1. In a process of developing an irnagewise-exposed photographic element comprising a support and at least one image dye-providing layer unit thereon which con tains a light-sensitive silver halide emulsion having associated therewith a color coupler, which process includes (1) development of the imagewise-exposed silver halide emulsion to provide an imagewise distribution of metallic silver and inbibition of a color-developing agent in said photographic element, and then (2) contacting said photographic element with an amplifier composition which represses substantially additional net silver development, said amplifier solution containing a cobalt(I1I) metal complex having a coordination number of '6, and said amplifier solution being maintained in contact with said photographic element under conditions which reduce said cobalt(I1I) to cobalt(II) and in turn oxidize said colordeveloping agent to provide an increase in dye density with dye produced from said coupler in the areas corre sponding to the imagewise distribution of said metallic silver, the improvement comprising including in said amplifier composition an Fe(III) chelate of an aminocarboxylic acid.

2. A process according to Claim 1 wherein said amplifier bath contains a suflicient quantity of development restrainer to repress substantially any further net silver development.

3. A process according to Claim 1 wherein said colordeveloping agent imbibed in said photographic element is an aromatic primary amino compound.

4. A process according to Claim 1 wherein said development of the imagewise-exposed silver halide emulsion is carried out in a liquid which is substantially free from cobalt(I1I) complex salts.

5. A process according to Claim 1 wherein said amplifier bath is substantially free from silver halide solvents or contains less than 30% by weight of the silver halide solvent which would be necessary to .fix said silver halide emulsion.

6. A process according to Claim 1 wherein the chelate is ferric ethylenediamine tetraacetic acid or ferric nitrilotriacetic acid.

7. A process according to Claim 1 wherein said chelate is present in said amplifier solution at a concentration from 1 10- g./l. up to the solubility limit of said chelate.

8. A process according to Claim 1 wherein said photographic element is a multicolor photographic element comprising at least two color-providing layer units, each of which contains a silver halide emulsion having associated therewith a photographic color coupler in at least a 40% stoichiometric excess based on silver.

9. A process according to Claim 1 wherein said photographic element is a photographic element comprising at least one image dye-providing layer unit which contains a silver halide emulsion having associated therewith a water-insoluble image dye-providing coupler dissolved in a coupler solvent wherein said coupler is present in at least a 40% stoichiometric excess based on effective silver.

10. A process according to Claim 8 wherein each said color-providing layer unit contains a silver halide emulsion at a concentration of less than 30 mg. silver/ft.

11. A process according to Claim 1 wherein the halide concentration of all silver halide emulsions in said element is less than 3 mole percent iodide.

12. A process according to Claim 2 wherein said development restrainer is substantially free from ionic iodide groups and free mercapto groups.

13. A process according to Claim 2 wherein said development restrainer is the combination of from about 0.01 to about 2 g./l. of a benzotriazole and from 2 g. to about 40 g./l. of an alkali metal bromide.

14. A process according to Claim 1 wherein said amplifier bath contains from about 2 g. to about 40 g./l. of an alkali metal bromide.

15. A process according to Claim 1 wherein said cobalt(I1I) metal complex is a cobalt hexammine salt.

16. A process according to Claim 1 wherein said chelate has the following structure:

L is an alkylene group, a substituted alkylene group, a cycloalkylene group or a substituted cycloalkylene p;

x is 0, 1 or 2;

R can be an alkylene group or a substituted alkylene group; and

R and R which can be the same or diiferent, can each be a hydrogen atom, an alkyl group, a substituted alkyl group, an aralkyl group, a substituted aralkyl group, an aryl group or a substituted aryl group.

References Cited UNITED STATES PATENTS 3,748,138 7/1973 Bissonette 96-663 RONALD H. SMITH, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R.

Patent No.3 ,8 L6, 130

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated November 5, 197

: 1nventor(s) Michael Dennis Purol and Richard Joseph Malloy "Column 1, line 12, "providng" should read --providing--; line It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

16 "eye" should read dye-e. Column 2, line 11, after "cobalt(III)", --complex-- should be inserted; line 18,

"process" should read "processed"; line 28, "distribtuion" :should read --distribution-; line 29 "in" (first occurrence) should read --and--. Column 4, line L9, that part of formula ,reading "hydorxy" should read --hydro'Xy--. Column 7, line 60,

"ponits" should read "points"; Column 8, line 45, before "as", --such-- should be inserted-- Column 10 line 61, that part of formula reading "5-[oa" should read "5-H Column @ll, line 23, "sllfate" should read sulfate. Column 12, line ll, that part of formula reading "methovyethyl" should read v ;methoxyethyl-.

Signed and sealed this 11th day of February 1975.

(SEAL) Attest:

C. MARSHALL DANN Commissioner of Patents and Trademarks RUTH C. MASON Attesting Officer 

1. IN A PROCESS OF DEVELOPING AN IMAGEWISE-EXPOSED PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT AND AT LEAST ONE IMAGE DYE-PROVIDING LAYER UNIT THEREON WHICH CONTAINS A LIGHT-SENSITIVE SILVER HALIDE EMULSION HAVING ASSOCIATED THEREWITH A COLOR COUPLER, WHICH PROCESS INCLUDES (1) DEVELOPMENT OF THE IMAGEWISE-EXPOSED SILVER HALIDE EMULSION TO PROVIDE AN IMAGEWISE DISTRIBUTION OF METALLIC SILVER AND INBIBITION OF A COLOR-DEVELOPING AGENT IN SAID PHOTOGRAPHIC ELEMENT, AND THEN (2) CONTACTING SAID PHOTOGRAPHIC ELEMENT WITH AN AMPLIFIER COMPOSITION WHICH REPRESSURES SUBSTANTIALLY ADITIONAL NET SILVER DEVELOPMENT, SAID AMPLIFIER SOLUTION CONTAINING A COBALT(III) METAL COMPLEX HAVING A CORDINATION NUMBER OF 6, AND SAID AMPLIFIER SOLUTION BEING MMAINTAINED IN CONTACT WITH SAID PHOTOGRAPHIC ELEMENT UNDER CONDITIONS WHICH REDUCE SAID COBALT (III) TO COBALT (II) AND IN TURN OIDIZE SAID COLORDEVELOPING AGENT TO PROVIDE AN INCREASE IN DYE DENSITY WITH DYE PRODUCED FROM SAID COUPLER IN THE AREAS CORRESPONDING TO THE IMAGEWISE DISTRIBUTION OF SAID METALLIC SILER, THE IMPROVEMENT COMPRISING INCLUDING IN SAID AMPLIFIER COMPOSITION AN FE(III) CHELATE OF AN AMINOCARBOXYLIC ACID. 